Doctors say giving Trump the antiviral drug remdesivir is a sign his infection may be serious — even though the timeline is still unclear

• President Trump is being treated for the coronavirus at Walter Reed Medical Center after announcing his diagnosis on Friday.
• Trump received an IV infusion of the antiviral drug remdesivir on Friday.
• A White House official told CBS News that Trump also received an experimental antibody cocktail on Thursday evening, but Trump's medical team has suggested that he received the drug either earlier or later than that.
• Regardless of the timing, a remdesivir treatment suggests Trump's illness could be serious, doctors say.
• Visit Business Insider's homepage for more stories.

President Donald Trump is "doing very well" at Walter Reed Medical Center, the president's doctors said on Saturday morning. After his Friday announcement that he'd tested positive for the coronavirus, Trump was reportedly experiencing a low-grade fever, cough, lethargy, and nasal congestion. 

"At this time, the team and I are extremely happy with the progress the president has made," White House physician Sean Conley said on Saturday.

Trump received an IV infusion of the antiviral drug remdesivir on Friday. The repurposed Ebola treatment is one of two FDA-authorized therapies for coronavirus patients. It's typically given to hospitalized patients who have developed a severe infection but don't require breathing machines or ICU admission.

That has some doctors worried that Trump's symptoms could be more than mild.

Their suspicion is bolstered by the fact that prior to receiving remdesivir, Trump also got a dose of an experimental antibody cocktail made by the biotech company Regeneron.

"The fact that he has been given two interventions already speaks to something that's probably going on," Dr. Panagis Galiatsatos, a pulmonary physician at Johns Hopkins Bayview Medical Center, told Business Insider.

Regeneron's drug was recently found to reduce a patient's viral load — the amount of virus in the body — in a clinical trial of 275 people. Those who got the treatment also saw their symptoms resolve more quickly than those who received a placebo. But the therapy hasn't been authorized by the FDA, and it hasn't been tested in combination with remdesivir. So doctors aren't sure how they will work together.

Multiple doctors told Business Insider, however, that administering remdesivir and the antibody cocktail early makes sense, given that Trump's age and weight make him more vulnerable to severe infection. 

"The thought is if you can reduce the viral burden with an antiviral early on, then maybe the progression will be halted in some way," Dr. Mangala Narasimhan, who oversees ICU care at Northwell Health in New York, said.

A confusing, contradictory timeline of Trump's infection and treatment

On Saturday, Trump's medical team offered a shaky timeline of when the antibody cocktail was actually administered. Dr. Ben Garibaldi told reporters that the president received the cocktail 48 hours prior to the press conference, suggesting that Trump took the drug around noon on Thursday. That was well before his diagnosis was revealed to the public.

But Conley then released a statement shortly after saying the president received that antibody cocktail on Friday after testing positive on Thursday night. A White House official, meanwhile, told CBS News that the drug was administered on Thursday evening.

Doctors and officials have also given conflicting reports about the state of Trump's health overall.

Conley told reporters on Saturday that the president has not had any difficulty breathing and does not require oxygen. But he declined to say whether Trump has received supplemental oxygen for his illness at any point so far, and the Associated Press reported that Trump was indeed given supplemental oxygen at the White House on Friday, prior to going to the hospital.

The New York Times reported that the president had trouble breathing on Friday, citing two people close to the White House. And White House chief of staff Mark Meadows told the Associated Press, meanwhile, that Trump had a "very concerning" period on Friday, adding that the next 48 hours would be "critical" for his treatment.

Remdesivir is typically reserved for severe cases

On average, it can take a week or more for a coronavirus patient to be admitted to the hospital after symptoms arrive. It's still unclear when Trump got infected, but the president may have been showing early symptoms on Wednesday, Bloomberg News reported. 

Galiatsatos said the fact that doctors administered remdesivir shortly after the antibody cocktail is a sign that Trump may have mounted a "chaotic" inflammatory response. 

"If your immune system is doing well, you don't want to stop that. You don't want to interfere with your remdesivir or your steroids," Galiatsatos said. "If they felt the need to pull the trigger on that, my suspicion is they're picking up some signals that he might not do well."

But on Saturday, Conley explained his decision to administer remdesivir as simply pursuing all options.

"I didn't want to hold anything back," he said. "If there was any possibility that it would add value to his care and expedite his return, I wanted to take it."

'Survival is just chapter one'

Trump's doctors plan for him to complete a standard five-day course of remdesivir. In a memo on Friday, Conley said Trump was also taking zinc, Vitamin D, melatonin, aspirin, and an anti-heartburn medicine. Studies have shown that Vitamin D could help reduce the severity of COVID-19 infections. 

"He's doing so well, but with the known course of the illness, day seven to 10 we get really concerned about the inflammatory phase," Conley said. "Given that we provided some of these advanced therapies so early in the course, a little bit earlier than most of the patients we know and follow, it's hard to tell where he is on that course. Every day we're evaluating, does he need to be here, what does he need, and where is he going?"

He added that "all indicators are that [Trump will] remain off of oxygen going forward."

For most coronavirus patients who are hospitalized, Galiatsatos said, their conditions get worse before they get better. Older men with preexisting health problems tend to decline more quickly than most, he added. 

"If he follows the most common, critical care phenotype, he's going to get sick, he's going to plateau in a very horrible purgatory, like a breathing machine and so forth, for weeks before he then turns around," Galiatsatos said.

Trump's prognosis is not publicly available, however. It's also difficult for independent experts to assess, given the missing information about when the president was diagnosed and treated, as well as conflicting accounts of his need for supplemental oxygen. If doctors announce they've administered a steroid, Galiatsatos said, that will be a sign that Trump's condition has probably worsened.

Regardless of what happens going forward, he added, patients who are hospitalized with the coronavirus typically face a long recovery.

"Survival is just chapter one," Galiatsatos said. "What doesn't kill you from COVID-19 doesn't make you stronger. It makes you weaker. So he's got to recognize that, if he survives kind of the worst of this, he's got a long way to recover."

Andrew Dunn contributed reporting.